The parent cases referred to above, the contents of which are incorporated by reference herein, describe the use of fugitive hydrocarbon fuels which emanate from various sources and which fugitive gas can be used as a supplementary or primary fuel for an engine. In general, the previous applications focus on using such fuels in their undiluted states; that is, without the addition of air to the hydrocarbons.
The use of fugitive hydrocarbon gases with air mixed with the hydrocarbon gas is also useful since, otherwise, such diluted fugitive gases would be wasted. There are several sources of fugitive gases where the gases are inherently diluted such as building gases and gases from dehydrator units. Additionally, sources of fugitive gases that might otherwise provide undiluted gases, may have leaks that are difficult to find or eliminate such as compressor crankcases and these gases become diluted. Since no check or pressure relief valves are required for the vent gas collection system used with diluted fugitive gases, the component cost of a diluted fugitive gas system is less an undiluted fugitive gas configuration.
It would therefore be advantageous to allow diluted fugitive gases to be used as a fuel. To that end, it is required that the hydrocarbons in the gases emanating from the sources of such diluted fugitive gases be estimated.
Engines, turbines and heating units using natural gas and other gaseous fuels are known and are used extensively, particularly in locations where natural gas production takes place. Such engines and turbines range from 30 HP to over 10000 HP and may conveniently be used in powering gas compressors, pumps and electric generators and which powered equipment is normally associated with natural gas production. The heating units are used in a wide range of industrial processes. The natural gas or other gaseous fuel is introduced directly to the cylinder of the natural gas engine or to the intake manifold. A spark ignitor is typically used to ignite the combustible natural gas and an air supply adds the air necessary to support the combustion.
The gaseous fuel used for such engines, turbines or heating units comes from a fuel source such as natural gas and the air to support the combustion of the gas comes from the atmosphere. Normally, the gaseous fuel is under pressure and appropriate ducting extends from the pressurized fuel supply to the engine. A carburetor, valves or an electronic control mechanism is used to regulate the quantity of natural gas provided to the engine and the quantity of air added to the natural gas for efficient combustion.
Various production processes in natural gas production result in losses of combustible gases. Such gaseous losses typically occur from compressors, particularly where the packing is old or otherwise deficient, from pneumatic instrumentation utilising natural gas, from initiating or starting engine procedure using natural gas, from gas dehydration units, from engine crankcases and from petroleum liquid storage tanks. These gas losses, typically called “fugitive and/or vent emissions”, are usually passed to the atmosphere or to a stack for burning. In either case, they are lost and the energy content of these gases which can be considerable, is similarly lost. It is disadvantageous and energy deficient to lose these fugitive or vent gases.
It is known to use natural gas as a supplementary fuel for a diesel engine by adding natural gas to the intake air. This natural gas, however, is not a fugitive or vent gas and the gas is maintained under pressure as a normal fuel source. The use of such fuel does not lower costs by using a fuel normally lost or deliberately discarded and such a fuel is not an emission resulting from venting or escaping gas. Fugitive gases have been collected and used as a fuel source but such gases have been collected and put under pressure. Such gases are not used as a supplementary fuel source.